<template>
    <view>
        <view class="title">请在下面输入签名：</view>
        <canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove" @touchend="touchend"></canvas>
        <view class="footer">
            <view class="left" @click="finish">完成</view>
            <view class="right" @click="clear">清除</view>
        </view>
    </view>
</template>

<script>
    var x = 20;
    var y = 20;
    export default {
        data() {
            return {
                ctx: '', //绘图图像
                points: [] //路径点集合 
            }
        },
        onLoad() {
            this.ctx = uni.createCanvasContext("mycanvas", this); //创建绘图对象

            //设置画笔样式
            this.ctx.lineWidth = 4;
            this.ctx.lineCap = "round"
            this.ctx.lineJoin = "round"
        },
        methods: {
            //触摸开始，获取到起点
            touchstart: function(e) {
                let startX = e.changedTouches[0].x;
                let startY = e.changedTouches[0].y;
                let startPoint = {
                    X: startX,
                    Y: startY
                };

                /* **************************************************
                	#由于uni对canvas的实现有所不同，这里需要把起点存起来
                 * **************************************************/
                this.points.push(startPoint);

                //每次触摸开始，开启新的路径
                this.ctx.beginPath();
            },

            //触摸移动，获取到路径点
            touchmove: function(e) {
                let moveX = e.changedTouches[0].x;
                let moveY = e.changedTouches[0].y;
                let movePoint = {
                    X: moveX,
                    Y: moveY
                };
                this.points.push(movePoint); //存点
                let len = this.points.length;
                if (len >= 2) {
                    this.draw(); //绘制路径
                }

            },

            // 触摸结束，将未绘制的点清空防止对后续路径产生干扰
            touchend: function() {
                this.points = [];
            },

            /* ***********************************************
            #   绘制笔迹
            #	1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
            #	2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
            #	3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
            ************************************************ */
            draw: function() {
                let point1 = this.points[0]
                let point2 = this.points[1]
                this.points.shift()
                this.ctx.moveTo(point1.X, point1.Y)
                this.ctx.lineTo(point2.X, point2.Y)
                this.ctx.stroke()
                this.ctx.draw(true)
            },

            //清空画布
            clear: function() {
                let that = this;
                uni.getSystemInfo({
                    success: function(res) {
                        let canvasw = res.windowWidth;
                        let canvash = res.windowHeight;
                        that.ctx.clearRect(0, 0, canvasw, canvash);
                        that.ctx.draw(true);
                    },
                })
            },

            //完成绘画并保存到本地
            finish: function() {
                uni.canvasToTempFilePath({
                    canvasId: 'mycanvas',
                    success: function(res) {
                        let path = res.tempFilePath;
                        uni.saveImageToPhotosAlbum({
                            filePath: path
                        })
                    }
                })
            }
        },
    }
</script>

<style>
    .title {
        height: 50upx;
        line-height: 50upx;
        font-size: 16px;
    }

    .mycanvas {
        width: 100%;
        height: calc(100vh - 200upx);
        background-color: #ECECEC;
    }

    .footer {
        font-size: 16px;
        height: 150upx;
        display: flex;
        justify-content: space-around;
        align-items: center;
    }

    .left,
    .right {
        line-height: 100upx;
        height: 100upx;
        width: 250upx;
        text-align: center;
        font-weight: bold;
        color: white;
        border-radius: 5upx;
    }

    .left {
        background: #007AFF;
    }

    .right {
        background: orange;
    }
</style>
